1. Field of the Invention
The present invention relates to opening and closing apparatus for opening and closing a rear gate (tail gate) pivotally attached to a vehicle body via a horizontal hinge shaft in such a manner as to open and close freely with a driving unit installed on a side of the vehicle body.
2. Related Art
Among conventional automotive rear gate opening and closing apparatuses, there is an automotive rear gate opening and closing apparatus as shown in FIGS. 5 and 6. FIG. 5 is a side view of a main part of a conventional rear gate opening and closing apparatus, and FIG. 6 is a plan view thereof.
Namely, in the conventional automotive rear gate opening and closing apparatus, a motor 102 which can rotate both in normal and reverse directions, a gearbox 103 in which a pinion 104 for reducing the rotating speed of the motor 102 for output is provided and a driving unit 106 having a rack 105 which meshes with the pinion 104 so as to reciprocate in longitudinal directions are installed within a space formed between a lower surface of a roofpanel 101 and a roof trim, not shown. In addition, a rear end portion of the rack 105 is connected to a rear gate 108 pivotally attached to a vehicle body via a transversely (vertically in FIG. 6) extending hinge shaft 107 in such a manner as to open and close freely, whereby by virtue of the rotation of the pinion 104, the rear gate 108 is made to swing in an opening direction by moving the rack 105 rearward (rightward in FIGS. 5 and 6) and the rear gate 108 is made to swing in a closing direction by moving the rack 105 forward (leftward in FIGS. 5 and 6).
With the conventional opening and closing apparatus as described above, however, the transverse dimension of the overall driving unit 106 is increased due to the motor 102 being connected to one side of the gearbox 103 so as to extend transversely and the rack 105 being supported on the other side of the gearbox 103, and in order to minimize the sacrifice of the space within the passenger compartment, it has been not easy to secure a space for installing the driving unit 106.
In particular, in an opening and closing apparatus in which a clutch, not shown, for connecting and disconnecting a power transmission path between the motor 102 and the pinion 104 is accommodated in the gearbox 103, the transverse dimension of the gearbox 103 is increased, and hence the transverse dimension of the overall driving unit 106 is increased further.
Further, according to the conventional opening and closing apparatus as described above, since the motor 102 is connected to the side of the gearbox 103 at the position closer to the rear end thereof and the pinion 104 is pivotally attached to the longitudinally central portion of the gearbox 103, the motor 102 and part (the rear end portion) of the gear box 103 are interposed between a connecting point a between the rack 105 and the rear gate 108 side and a meshing point b between the rack 105 and the pinion 104. Those constituent members so interposed constitute obstacles and hence need to be spaced away from the rear roof rail constituting the opening in order to avoid the interference therewith, and this results in a construction in which the meshing point b and the connecting point a cannot get closer to each other.
As a result, a distance L1 between the connecting point a and the meshing point b is increased, and hence the overall length of the rack 105 needs to be increased in the longitudinal direction.
However, the longer the overall length of the rack 105 becomes, the easier the rack 105 buckles due to a compressive force applied to the rack 105 when the rack 105 is moved rearward so as to push the rear gate 108 in the opening direction, and therefore, extending the overall length of the rack 105 is disadvantageous in terms of strength.
In addition, the roof trim protrudes to the inside of the passenger compartment by a distance equal to the overall length of the rack 105, and therefore, the space inside the passenger compartment gets narrower.